1. Field of the Invention
The present invention relates generally to signal amplifiers and applications thereof.
2. Description of the Related Art
The accuracy of many electronic systems is degraded if critical amplifiers cannot supply transient currents that are sufficient to accurately amplify input signals. For example, signal amplifiers are often required to drive loads which partially or wholly comprise a capacitive load. To generate an accurate amplified version of an input signal across these capacitive loads, the amplifier must provide high transient currents which can accurately alter the output signal's amplitude. Limitations in these transient currents leads directly to degraded performance.
An exemplary amplifier is an amplifier in a multiplying digital-to-analog converter (MDAC) of a pipelined analog-to-digital converter system. Such systems are configured with successive converter stages which each convert an analog input signal to respective digital bits of a final digital code that corresponds to the analog input signal. Except for a final converter stage, each converter stage also passes a residue signal to a succeeding stage for further conversion processing.
The residue signal is the difference between the analog signal presented to the stage and the analog equivalent of this stage's respective digital bits. Errors in generation of the residue signal cannot be corrected and, accordingly, they contribute directly to errors in the corresponding digital code.
Integrated circuit MDACs are often configured with capacitors that are switched in a first portion of each sample period to receive a charge from the residue signal of the preceding converter stage and switched in a second portion of each sample period to transfer this charge to an output capacitor. These charging and transferring processes are generally accomplished with the aid of an MDAC amplifier and the accuracy of these processes is dependent upon the ability of this amplifier to provide high-level transient currents to the MDAC capacitors. This is but one example of a need for amplifiers having enhanced transient performance.